A conventional motor-driven shutter is driven in response to an exposure value EV which is calculated from a shutter exposure time TV, a stop value AV, film sensitivity SV, object luminance BV, and so forth. The exposure value EV is calculated by a method called the APEX (Additive System of Photographic Exposure), which is able to perform operation processing in a camera with an additive operation, since the shutter stop values and so forth form a multiple series.
The exposure characteristics of the motor-driven shutter are controlled by exposure data EDn which correspond to calculated exposure values EVn. When the exposure data EDn are interpolated with respect to the exposure values EVn in a multiple series for instance, the exposure data EDn become four times as large as the multiple series. Thus, a drawback arises that the exposure data EDn requires an increase in the storage capacity of a ROM to accommodate the additional data.
Further, there is another drawback in that the required increase of ROM capacity increases the cost of the processor IC which contains the ROM, and different exposure data EDn have to be entered in advance for every type of unit, depending upon the circumstances.